Hydraulic transmission device suitable for constituting a compact hydraulic starter motor

ABSTRACT

A hydraulic transmission device for a machine, including a declutchable hydraulic motor having radial pistons, and including a cam that is secured to a casing, and a cylinder block and an internal fluid distributor that are disposed in the casing; a hydraulic pump including a drive member; and fluid exchange couplings; in which device the casing and the distributor are mounted to rotate relative to a stationary support about an axis of rotation, whereas the cylinder block is fastened to said support. In some embodiments, the drive member of the pump is constrained to rotate with the casing of the motor, and in that a delivery orifice of the pump is connected to one of said couplings.

The present invention relates to a hydraulic transmission device for a machine, which device comprises:

-   -   a hydraulic motor declutchable by dog clutch having radial         pistons, and including a cam that is secured to a casing, and a         cylinder block and an internal fluid distributor that are         disposed in the casing;     -   a hydraulic pump including a drive member; and     -   a plurality of fluid exchange couplings;     -   in which device the casing and the distributor are mounted to         rotate relative to a stationary support about an axis of         rotation, whereas the cylinder block is fastened to said         support.

The term “stationary” support is used herein to mean a support that is a portion of the device that does not rotate. The support is therefore designed to be stationary relative to the machine. It mechanically holds the cylinder block and more generally the hydraulic motor on the machine. Preferably, the cylinder block is fastened rigidly to the support.

The casing is the casing of the hydraulic motor; in particular, it houses the cylinder block and the fluid distributor.

The fluid exchange couplings are couplings via which the device exchanges fluid with other hydraulic components. For example, the couplings are usually connected to a fluid reservoir or to a fluid accumulator, via fluid feed and/or fluid discharge ducts.

The invention relates more particularly to a hydraulic transmission of the above-mentioned type that can be used to drive a machine member or a tool rapidly in rotation, with drive of which member or tool then being taken over by another motor or engine above a certain speed threshold. In particular, the machine or a tool may have high inertia.

In particular, such devices are used to serve as starter motors for internal combustion engines, e.g. diesel engines.

One known solution for obtaining a starter motor consists in using an electric motor powered by a battery. However, electric starter motors and batteries are not suitable for very large numbers of starting operations. Today, in order to save fuel, it is desired to be able to stop an engine as soon as it is no longer needed, even if it is then re-started almost immediately afterwards. With such use, the number of starts to which the engine is subjected is very high: thus, the number of starts that the starter motor needs to perform is considerably higher than the number of starts that an electric starter motor can perform.

A known alternative consists in using a hydraulic motor as a starter motor. Such a motor can constitute a starter motor that is effective for an internal combustion engine, particularly when the internal combustion engine serves to drive a load having high inertia: a hydrostatic starter motor has very high power density (per unit volume), which enables it to be more compact than an electric starter motor. Using a hydrostatic motor for a starter motor is also advantageous because it is robust, and has a long life, enabling it to perform a large number of starts.

A hydraulic motor can, in particular, be used as a starter motor for an internal combustion engine, such as, for example, a vehicle engine, in particular for a vehicle of the urban transport type, having a large weight. When the engine needs to supply torque for moving the vehicle that is zero or low, the engine is then used to fill an accumulator with fluid under pressure by means of a pump. When the vehicle is at a standstill or when the engine is idling, said engine is switched off; by means of the accumulator, the engine is re-started by the hydraulic motor, actuated by the fluid coming from the accumulator.

A known embodiment of a hydraulic starter motor for a diesel engine is shown in FIG. 1. In this figure, the valves, the monitoring means, the control means, the safety means, etc. are not shown, unless otherwise indicated.

FIG. 1 shows a diesel engine 10 provided with a hydraulic transmission device 12 serving as a starter motor for the engine.

The device 12 comprises an accumulator 14 for accumulating pressurized fluid, a pump 16, a hydraulic motor 18, and a reservoir 20 of fluid at atmospheric pressure.

The accumulator 14 is connected to the hydraulic motor 18 via a duct 22 for the purpose of feeding the motor 18 with pressurized fluid in order to start the engine 10. When the motor 18 is fed in this way, the fluid, after passing through the motor 18, is directed towards the reservoir 20 via a discharge duct 24. The casing 26 of the motor 18 is mounted in the end of the crankshaft of the engine 10. The casing 26 is a rotary casing that is the outlet member of the motor 18. Thus, when the motor 18 is fed with pressurized fluid, the casing 26 starts rotating and, in turn, drives the crankshaft of the engine 10 in rotation, thereby starting the engine 10.

In addition, a belt 28 that engages in external grooves formed respectively in the casing 30 of the pump 16 and in the casing 26 of the motor 18, constrains the pump 16 and the motor 18 to rotate with each other. For this reason, when the crankshaft of the motor 10 rotates, the casing 26 of the motor 18 and the casing 30 of the pump 16 also rotate.

In addition, the pump 16 is connected to the reservoir 20 via a suction feed duct 32, and to the accumulator 14 via a filling duct 34.

As indicated above, throughout all of the operating stages of the engine 10, the pump 16 is actuated (i.e. its casing 30 is driven in rotation). Thus, while the engine 10 is running, the pump 16 pumps fluid into the reservoir 20 in such a manner as to fill the accumulator 14, via the ducts 32 and 34. Filling of the accumulator is caused to stop by a valve 36 interposed between the accumulator 14 and the ducts 22 and 34.

The device 12 operates as follows:

When the engine 10 is off, the accumulator 14 is, in principle, full.

In order to start the engine 10, the accumulator 14 is caused to be emptied into the reservoir 20 via the motor 18. The pressurized fluid from the accumulator actuates the motor 18; the casing 26 of the motor 18 starts rotating, thereby, in turn, causing the crankshaft of the engine 10 to rotate, and causing the engine 10 to start. The engine 10 is then operating.

While the engine 10 is operating, and via the belt 28, the casing 26 of the motor 18 drives the casing 30 of the pump 16. The pump 16 actuated in this way then recharges the accumulator 14 with pressurized fluid.

In general, the hydraulic starter system 12 acts in addition to an electric starter system.

Although that hydraulic device 12 operates satisfactorily, it is relatively voluminous, which makes it difficult to install on many pieces of equipment, in particular on many engines such as the engine 10.

More generally, known hydraulic motors and the components of the circuit necessary for feeding them are not optimized for being used as starter motors for vehicle engines or other types of machinery. Hydraulic motors require large numbers of pipes to be provided, a booster pump to be installed, and that booster pump needs to be driven by an outlet shaft of the engine or via an additional electrical drive. As a result, installing a hydraulic motor, and the circuit that accompanies it, as a starter motor for an engine is an operation that is complicated.

However, an example of a hydraulic starter motor that offers a certain amount of compactness is disclosed by Document GB 1 395 901.

That document discloses a hydraulic starter motor associating a hydraulic motor having radial pistons with a pump making it possible to charge an accumulator. The motor is of the type having a stationary casing, with a rotary shaft to which the cylinder block is fastened. The outlet member of the motor is a coupling part that is fastened at the end of the shaft of the motor. The presence of this part induces additional length and additional complexity for the hydraulic starter motor.

When the pressure inside the accumulator becomes low, a valve device makes it possible to activate a hydraulic clutch interposed between the shaft of the motor and the drive member of the pump. The shaft of the motor then drives the pump; said pump rotating then makes it possible to recharge the accumulator.

Thus, although the motor is placed in the vicinity of the pump, that starter motor suffers from the drawback of being large in size and highly complex, in particular because of the clutch interposed between the motor and the pump.

An object of the invention is thus to propose an improved hydraulic transmission device of the type presented in the introduction, and that is suitable for constituting a hydraulic starter motor that is relatively simple and that is compact by being coupled to an accumulator and to a reservoir of fluid.

This object is achieved in the device described in the introduction by the facts that the drive member of the pump is constrained to rotate with the casing of the motor, and that a delivery orifice of the pump is connected to one of the couplings of the device.

By means of this connection, the pump is suitable for delivering fluid under pressure via said coupling; as a result, the pump is suitable for being connected to an accumulator in order to fill it with fluid under pressure.

In addition, the pump is driven in rotation by the casing (directly or indirectly); it can thus be arranged in the immediate vicinity of the motor and be incorporated therein.

In addition, since the casing is a rotary casing, it constitutes, directly or indirectly, the outlet member of the starter motor, which makes it unnecessary to use a coupling part that is fastened at the end of the outlet shaft of the motor, as in the above-described prior art example.

Advantageously, the invention procures a device that is not only compact, but that is also inexpensive to produce, due to the reduced length of the connecting ducts between the pump and the hydraulic motor, due to the reduction in the number of connection components, and due to a reduced number of operations for assembling it onto engines, including a reduction in the number of hydraulic interconnections to be made.

In the above definition, the expression “constrained to rotate with” means constrained continuously to rotate with. Therefore, no clutch is interposed between the pump and the motor, and the pump is driven continuously whenever the motor is operating. The absence of any clutch procures considerable simplification compared with the above-mentioned prior art example.

In the device of the invention, the motor may be fastened to the support in various manners.

The support firstly holds the cylinder block. In addition, the casing and the distributor must be arranged in such a manner as to be able to rotate relative to the cylinder block. Finally, the distributor must, in addition, be situated facing the cylinder block in order to distribute fluid to the cylinders of the cylinder block.

In view of these technical constraints, the support may, in particular, be implemented in the following two embodiments:

In a first embodiment, the support has a preferably substantially cylindrical portion about which the distributor is arranged.

This substantially cylindrical portion may, in particular, advantageously be extended inside the cylinder block in order to enable the cylinder block to be held. The support may then be in the form of a support shaft (while being arranged essentially in the form of a shaft), this configuration presenting the advantage of being very compact. The substantially cylindrical portion may be of any shape that is generally circularly symmetrical, and that is sufficiently elongate to enable the distributor and, where applicable, the cylinder block to be disposed around the substantially cylindrical portion. This portion may thus, for example, be of generally conical shape.

In this embodiment, the cylinder block is held by the inside (when the support forms a shaft passing through the inside of the cylinder block) or at least in the vicinity of its axis of rotation. The distributor is disposed around the support. This embodiment is extremely compact while procuring effective mechanical holding of the cylinder block.

In a second embodiment, the support and/or the cylinder block is provided with an axial bore formed along the axis of rotation of the motor, inside which bore the distributor is disposed. The vicinity of the axis of rotation of the motor, in which vicinity the distributor is situated is then used for the fluid exchanges of the motor. Conversely, the volume situated radially around the distributor is occupied by the support and/or by the cylinder block in order to fasten the cylinder block to the support. The cylinder block is thus fastened to the support via its outside periphery.

This embodiment is advantageous if the motor is subjected to large bending forces, tending to misalign the cylinder block relative to the support.

The hydraulic motor generates drive torque (or braking torque) that should be transmitted to the machine to which the device is fastened. In order to enable the torque to be transmitted, the support may advantageously have a portion in the form of an arm through which at least one duct passes and which extends in a direction that is substantially perpendicular to the axis of rotation. Due to its shape, the portion in the form of a support arm is fastened to a stationary portion of the machine and thus serves as a connection arm, preventing any undesired rotation of the device relative to the machine.

Finally, the device of the invention may be incorporated into a starter system for a machine having a rotary drive member. In which case, the starter system includes a device as defined above and said drive member, the casing being constrained to rotate with said drive member. Preferably, the casing may be disposed in a portion of the rotary drive member. The machine to be driven may, for example, be an internal combustion engine, in particular a diesel engine.

In the device of the invention, the pump may be arranged relative to the support in various manners.

In one embodiment, an axis of rotation of the drive member of the pump coincides with the axis of rotation of the hydraulic motor. Transmission of movement between the hydraulic motor and the pump may thus be achieved via simple mechanical members, since these two components have drive members that are aligned along the same axis.

In one embodiment, the drive member of the pump is driven in rotation directly by the casing. The casing of the motor can then be the only rotary drive outlet member of the hydraulic motor, firstly to the pump and secondly to other components of the machine in which the device is incorporated (such as, for example, the crankshaft of the diesel engine of a vehicle).

In one embodiment, the device includes a drive shaft that is constrained to rotate with the cam and that is suitable for actuating the pump. This drive shaft may pass through the inside of the cylinder block and/or be fastened to the casing, and/or be disposed inside the support at least in part.

In one embodiment, the drive member of the pump is driven in rotation by a drive shaft that is fastened to the casing and that is disposed inside the support at least in part.

These two embodiments make it possible, in particular, for the drive member of the pump to have an axis that coincides with the axis of rotation of the motor.

In one embodiment, the pump is disposed inside the support at least in part and optionally entirely. The device is then particularly compact.

Arranging the pump inside the support, at least in part, facilitates incorporation inside the support of certain ducts connected to the pump and/or to the motor.

In one embodiment, the pump and the fluid exchange couplings are situated on the same side of the cylinder block of the motor, relative to the axis of rotation. This arrangement improves the compactness of the device.

In one embodiment, relative to the axis of rotation, the distributor is interposed between the fluid exchange couplings and the cylinder block.

In one embodiment, the device includes a drive shaft that is constrained to rotate with the cam, that passes through the inside of the cylinder block, and that is suitable for actuating the pump.

The mechanical connection constraining the cam and the shaft to rotate with each other is thus formed on the side (relative to the cylinder block) opposite from the distributor and/or from the fluid exchange couplings of the device.

The fluid distributor may also have any of the following characteristics, in isolation or in combination:

-   -   it may be a rotary distributor;     -   it may have a plane distribution face (in particular         perpendicular to the axis of rotation);     -   it may be disposed between the cylinder block and the pump, at         least in terms of position relative to the axis of rotation.

In one embodiment, at least an admission duct or a delivery duct of the pump and/or at least a feed duct or a discharge duct of the motor passes through the support. For example, a feed duct of the pump may be formed in the support and may connect an admission chamber of the pump to a coupling arranged on an outside surface of the support: thus, the pump is fed with fluid in a manner that is particularly simple and compact.

In one embodiment, a discharge duct of the motor and a feed duct of the pump meet at a junction situated in the support. Thus, these ducts are advantageously arranged compactly, and the device may have only three external couplings or orifices. In one embodiment, a feed duct of the pump and/or a discharge duct of the motor is formed in the support shaft and connects a coupling arranged on an outside surface of the support shaft to an internal space of the casing. Preferably, this duct serves both as the feed for the pump and as the discharge for the motor, when the fluid being discharged from the motor is discharged into the internal space of the casing.

In one embodiment, the fluid sucked up by the pump flows around the drive member of the pump before penetrating into the pump. It thus lubricates the drive member of the pump.

In particular, integrating the pump into the support may, in particular, be performed in such a manner as to enable the support to be lubricated by means of the fluid present inside the casing of the hydraulic motor. To this end, in the above-mentioned embodiment including a drive shaft for driving the pump and disposed at least in part inside the support, a feed passage of the pump via which passage a fluid feeding the pump passes may be formed between the drive shaft and the support. Fluid passing through this passage cools and lubricates the support. In order to convey the fluid into the feed passage, a feed duct of the pump may be formed in the support and may connect an internal space of the casing to the feed passage.

In one embodiment, the device may then include a fluid supply duct making it possible to inject a feed fluid for feeding the pump into said internal space; said internal space being, in addition, connected to said feed passage via a feed duct making it possible to feed the feed passage with fluid; an orifice of the feed duct in the internal space of the casing and an orifice of the supply duct in the internal space being disposed axially on either side of the cylinder block.

The fluid supply duct may, for example connect a coupling arranged on an outside surface of the support to the internal space of the casing. This supply duct serves, in particular, to bring fluid feeding the pump (or a portion thereof) into the internal space. By disposing the orifice of the feed duct in the internal space of the casing and the orifice of the supply duct in the internal space axially on either side of the cylinder block, the feed fluid of the pump, coming from the fluid supply duct, is caused to sweep through the cylinder block (or at least to pass from one side of the cylinder block to the other) in order to come to feed the pump. This sweeping thus enables the cylinder block to be cooled effectively.

In addition, when the motor is brought to rotate in one direction only, in one embodiment, the fluid discharge of the cylinder block takes place into an internal space of the casing. This enables the motor arrangement to be particularly simple. The feed of the motor may also be implemented very simply: a single annular groove can feed the motor with fluid. This single groove can be formed in an outside surface of the support.

In order to incorporate the pump into the support, it is preferable to choose a pump that is as compact as possible. Preferably, a pump is chosen that has its largest transverse dimension that is perpendicular to the axis of rotation less than the diameter of the cylinder block, e.g. a gear pump. The pump can then, in general, be disposed entirely inside the support.

As indicated above, the transmission device of the invention may, in particular be used for driving a rotary drive member of a machine in rotation. To this end, in one embodiment, in order to enable the casing to be coupled to a member to be driven, the casing has a flange, an external groove suitable for receiving a pulley belt, or else a set of teeth for receiving a chain or gearing. In a particularly advantageous arrangement, the casing may thus be fastened directly to one end of the crankshaft of an internal combustion engine.

The invention can be well understood and its advantages appear more clearly on reading the following detailed description of embodiments that are shown by way of non-limiting example. The description refers to the accompanying drawings, in which:

FIG. 1, described above, is a diagrammatic view of a diesel engine equipped with a known hydraulic device, serving as a starter motor;

FIG. 2 is a diagrammatic view of a diesel engine equipped with a hydraulic device of the invention, serving as a starter motor;

FIG. 3 is an axial section view of a first embodiment of a hydraulic device of the invention;

FIG. 4 is a view of the FIG. 3 hydraulic device in section perpendicular to its axis;

FIG. 5 is an axial section view of a second embodiment of a hydraulic device of the invention;

FIG. 6 is a view of the FIG. 5 hydraulic device in section perpendicular to its axis;

FIG. 7 is an axial section view of a third embodiment of a hydraulic device of the invention; and

FIG. 8 is a view of the FIG. 7 hydraulic device in section perpendicular to its axis.

FIG. 2 shows an engine 110 equipped with a hydraulic device 40 of the invention. Unless otherwise specified, the engine 110 and the device 40 are identical to the engine 10 and to the device 12 that are described above. Identical elements or elements having the same functions therefore bear the same numerical references in both figures, and are not described again below.

Implementing the invention in the hydraulic device 40 makes it possible to obtain an arrangement that is much more compact, as shown in FIG. 2, than in the example shown in FIG. 1. In the FIG. 2 embodiment, the device 40 includes a pump 44 that plays the same role as the pump 16; however, instead of being an external pump connected via a pulley to the motor 18, the pump 44 is an internal pump, incorporated in the hydraulic motor 42 (see FIGS. 3 and 4).

In addition, coupling of the hydraulic device 40 is simplified, and advantageously comprises only three ducts:

-   -   a duct 124 connecting an external coupling 70 of the motor 42 to         the reservoir 20;     -   a duct 22 connecting the accumulator 14 to a first coupling 72         of the motor 42; and     -   a duct 23 connecting the accumulator 14 to a second coupling 74         of the motor 42.

The ducts 22 and 23 are connected to the accumulator 14 via a valve 136.

FIGS. 3 and 4 are more detailed views of the device 40 that constitutes a first embodiment of the invention.

The device 40 includes a hydraulic motor 42 into which a hydraulic pump 44 is incorporated.

The motor 42 is a declutchable motor having radial pistons. It comprises:

-   -   a casing 46 made up of three portions, namely a cover 46A, a         lobed cam 46B, and a distribution casing 46C;     -   a cylinder block 48 and a fluid distributor 50 that are disposed         in an internal space 52 of the casing 46; and     -   a support in the form of a support shaft 54 to which the         cylinder block 48 is fastened rigidly.

The cylinder block 48 has cylinders 56 in which pistons 58 are slidably mounted. The pistons 58 are arranged in such a manner as to be capable of transmitting pressure to the inside surface of the cam 46B.

In known manner, the pressures exerted by the pistons 58 enable the motor 42 to develop drive torque. The drive torque is transmitted by the casing 46 that acts as an outlet member for the motor 42 to the equipment to which the motor 42 is mechanically coupled: In this example, the equipment is the crankshaft of the engine 110.

In order to transmit the torque generated by the hydraulic motor 42 to the diesel engine 110, the motor 42 has a flange 60 formed over an outside circumference of the distribution casing 46C. The flange 60 is bolted onto the crankshaft of the engine 110.

The components that are internal to the motor 42 are arranged in the following manner:

The distributor 50 is connected rigidly to the distribution casing 46C by means that are not shown.

In terms of axial position relative to the axis of rotation A, the distributor 50 is interposed between the fluid exchange couplings 70, 72, and 74, and the cylinder block 48. This arrangement enables the feed fluid of the motor to be transferred directly from the coupling 72 to the cylinder block 48 via the distributor 50, thereby forming a circuit that is short. The same applies for the fluid discharge via the distributor 50 transferring the fluid to the casing, thereby enabling the fluid to be removed directly via the coupling 70.

In addition, the pump 44 and the fluid exchange couplings 70, 72 and 74 are located on the same side of the cylinder block 48, relative to the axis of rotation A. This arrangement improves the compactness of the device.

In addition, the fluid distributor 50 is a rotary distributor and has a plane distribution face, perpendicular to the axis of rotation 51. It is disposed between the cylinder block 48 and the pump 44.

The pistons 58 are declutchable pistons. They are urged back into the cylinders 56 by springs 62, when the pressure inside the cylinders 56 is less than the pressure prevailing in the internal space 52 and when the difference between the two pressures exceeds a predetermined value that depends on the springs 62.

The casing 46 is held in position on the support shaft 54 by ball bearings 64 and 66 disposed on either side of the cylinder block 48. The bearings 64 and 66 hold the casing 46 and the distributor 50 in such a manner that they can rotate about the axis A of the support shaft 54.

The pump 44 is a compact gear pump. In a manner known per se, and as shown in FIG. 4, it has two toothed wheels 68A, 68B that mesh with each other and that pump the fluid passing through the pump 44.

The largest transverse dimension D of the pump 44, measured perpendicularly to the axis of rotation A is less than the diameter of the cylinder block and even than the radius of the cylinder block, thereby making it possible to incorporate the pump 44 without any particular difficulties into the support shaft 54.

The pump 44 is mounted in a bore (a chamber) formed in the support shaft 54. It is held in position by its cover 45, which is fastened to the end surface of the support shaft 54 by a screw 47.

The cover 45 is incorporated into the volume of the support shaft 54, in a manner such that the pump 44 is fully incorporated into the support shaft 54.

It is disposed inside a first end 54A of the support shaft, the cylinder block 48 being arranged around the opposite end 54B of the support shaft, and the distributor 50 being placed between the cylinder block 48 and the pump 44. This arrangement makes it possible to place the pump 44 as close as possible to the distributor 50 and thus to optimize the flow of fluid in the device 40.

The flow of fluid in the device 40 is described below.

Two sub-assemblies mainly exchange fluid: the motor 42 and the pump 44.

All of the exchanges of fluid of the device 40 take place via three couplings 70, 72, and 74 formed in the first end 54A of the support shaft 54.

For admission and delivery of fluid for the pump 44, two ducts 76 and 78 are formed in the end 54A of the support shaft. The pump admission duct 76 connects the coupling 70 to the admission chamber 441 of the pump 44. The pump delivery duct 78 connects the delivery chamber 440 of the pump 44 to the coupling 74.

For feeding fluid for the motor 42, a feed duct 80 provided with a bend is formed in the support shaft 54. This duct 80 connects the coupling 72 to an annular groove 75, formed in an outside circumference of the support shaft 54, inside the distributor 50.

The motor 42 operates as follows:

The fluid feeding the motor 42, coming from the accumulator 14 via the duct 22, is injected into the device 40 via the coupling 72. It is injected into the groove 75 via the duct 80. The distributor 50 has first distribution ducts 82. These ducts convey the fluid from the groove 75 to cylinder ducts 84 formed in the cylinder block 48, and via which the fluid is injected into the cylinders 56.

In a manner known per se, the distributor 50, which is driven in rotation by the casing 46, feeds the various cylinders 56 successively. The pistons 58 are driven in turn by the pressure in the cylinders 56 for causing the cylinders to come out; the pressure that they exert on the cam 46B generates drive torque. Thus, the injection of pressurized fluid from the accumulator 14 makes it possible to drive the casing 46 in rotation, thereby causing the engine 110 to start, via the flange 60.

While the pistons 58 are moving in, the fluid is removed from the cylinders 56 via the cylinder ducts 84; it is thus brought via second distribution ducts 86 into the internal space 52 of the casing 46.

A duct 88 passing through the support shaft 54 connects the internal space of the casing to the duct 76. This duct 88 joins the duct 76 that serves to feed the pump, at a T-junction situated in the support shaft. This junction thus splits the duct 76 into two portions, namely an external portion 76′ connecting the coupling 70 to the T-junction, and an internal portion 76″ connecting the T-junction to the admission chamber of the pump 441 (FIG. 4).

The duct 88 thus enables the fluid removed by the motor to be discharged from the internal space 52 to the outside of the support shaft, via the duct portion 76′ and the coupling 70. The fluid is directed from the coupling 70 into the reservoir 20 via the duct 124.

The pump 44 operates as follows:

The pump has a drive member or part 90 that enables it to be driven. This part 90 forms a shaft to which the toothed wheel 68A is fastened. The pump is disposed in the support shaft 54 in such a manner that the axis of the part 90 coincides with the axis of rotation A of the motor.

In addition, the device 40 has a drive shaft 92. The shaft 92 is constrained to rotate with the cam 46B, via the cover 46A. For this purpose, the shaft 92 is fastened (by screw-fastening) to the cover 46A of the motor 42. Naturally, any other mode of fastening the drive shaft 92 to the cover 46A may be used, such as, for example, a flattened drive finger having the shape of a screwdriver blade, etc. The axis of the shaft 92 also coincides with the axis of rotation A of the motor.

An axial cylindrical bore 94 is formed along the axis A in the support shaft 54 so as to enable the drive shaft 92 and the drive part 90 to pass through. The drive part 90 is constrained to rotate with the drive shaft 92 by means of a drive finger 96. The drive part 90 of the pump is therefore driven in rotation by the casing 46, via the drive shaft 92 and via the drive finger 96. The drive finger 96 makes it possible, in particular, for limited axial movement to take place along the axis A between the drive shaft 92 and the drive part 90. Such movement may be necessary as a function of the relative expansions of the shaft 92 and of the part 90.

Advantageously, the shaft 92 makes it possible to transmit the movement imposed by the motor on the cam 46B to the drive member 90 of the pump 44. This result is achieved by the fact that the shaft, connected to the cover 46A itself constrained to move with the cam 46B, connects said cover to the drive member 90 of the pump, by passing through the inside of the cylinder block 48.

The mechanical connection constraining the cam and the shaft to rotate with each other is thus formed by the cover 46A, situated on the side opposite from the distributor 50 and from the fluid exchange couplings 70, 72, and 74.

The pump 44 is supported by two bearings 98A and 98B, disposed axially on either side of the toothed wheels 68A, 68B.

When the pump is actuated, under the effect of the rotation of the gearing formed by the wheels 68A and 68B, the fluid is sucked up from the reservoir 20 via the duct 124 and via the duct 76. It is pumped by the toothed wheels 68A and 68B and transferred from the suction chamber 441 to the delivery chamber 440. It is thus delivered under pressure into the duct 78, and from there reaches the accumulator 14 via the duct 23. The pump thus fills the accumulator 14.

FIGS. 5 and 6 show a device 140 showing a second embodiment of the invention that is very similar to the first embodiment shown by FIGS. 3 and 4. The difference between the first and second embodiments lies in the path of the feed fluid for feeding the pump.

The hydraulic device 140 may be used as a hydraulic starter motor for an internal combustion engine, as in the first embodiment. It is incorporated into a motor in a manner exactly identical to the incorporation of the device 40 shown in FIGS. 2 to 4.

Unless otherwise indicated, the second embodiment may be considered as being identical to the first embodiment. Identical elements or elements having the same functions therefore bear the same numerical references in both embodiments.

In the second embodiment, the support shaft 154 has the following differences relative to the support shaft of the first embodiment:

Firstly, as regards the duct 76, only the external portion 76′ of said duct is formed. This portion 76′, in combination with the duct 88, forms a connection between the coupling 70 and the internal space 52 of the casing 46. Conversely, in this second embodiment, the internal portion 76″ of the duct 76 is not formed. There is therefore no direct communication between the coupling 70 and the admission chamber 441 of the pump 44.

It is through the internal space 52 that the fluid feeding the pump passes. To this end, for feeding the pump, a feed duct 100 is bored between the internal space 52 and the bore 94. This feed duct 100 is formed in the vicinity of the cover 46A, and preferably as close as possible thereto. The duct 100 enables fluid to pass from the internal space 52 towards the bore 94. Inside the bore 94, an annular feed passage 102 is provided by means of clearance provided between firstly the support shaft 154 and secondly the drive shaft 92 and the drive part 90. This clearance is calculated in such a manner that the feed passage cross-sectional area 102 is sufficient for feeding the pump.

In addition, a second feed passage 104 is provided at the end 154A of the support shaft that is on the same side as the pump 44. This second passage 104 connects the annular space 102 to the suction chamber 441 of the pump 44, and enables the fluid to pass through the annular space 102 to the chamber 44I, by going (radially) around the outside of the bearing 98B.

In this embodiment, the pump operates as follows: The fluid is sucked in by the pump from its suction chamber 441. The sucked-up fluid penetrates into the support shaft 154 via the coupling 70, goes via the ducts 76′ and 88, via the internal space 52 of the casing, via the duct 100, via the feed passage 102, via the second feed passage 104, and finally into the suction chamber 441. The advantage of this path is that the fluid sweeps through the internal space 52 of the casing, and through the annular space 102 between the passages 100 and 104. In doing so, it cools and lubricates the various elements, in particular all of the outside faces of the block 48, the drive shaft 92 and the drive part 90. To this end, the passage 100 is formed at the end 154B of the support shaft that is opposite from the end 154A that contains the pump 44; thus, the feed fluid of the pump travels through the annular passage 102 over nearly the entire length thereof, thus enabling the bore 94 to be lubricated and cooled in optimized manner.

The other aspects of the manner in which the device 140 of FIGS. 5 and 6 operates are identical to the aspects of the device 40 presented in the first embodiment. In the second embodiment, it can thus be observed that the ducts 88 and 76′ transport both the discharge fluid of the motor and the feed fluid of the pump. The two flows of fluid in opposite directions are compensated for in part in the ducts 88 and 76′.

FIGS. 7 and 8 show a device 240 illustrating a third embodiment of the invention that is very similar to the first two embodiments shown by FIGS. 3 to 6. The specificity of the third embodiment relative to the first two embodiments is the arrangement of the support (254) and, as a result, of the fluid exchange ducts of the device. In spite of these differences, the device 240 operates substantially identically to the manner in which the devices 40 and 140 operate.

Unless otherwise indicated, the third embodiment may be considered as being identical to the first embodiment. Identical elements or elements having the same functions therefore bear the same numerical references in the first, second, and third embodiments. However, certain elements of the third embodiment that are the subjects of specific description bear a numerical reference plus 200 relative to the element having the same function in the first embodiment.

The device 240 includes a hydraulic motor 242 into which a hydraulic pump 244 is incorporated.

The motor 242 is a declutchable motor having radial pistons that comprises:

-   -   a rotary casing 246 made up of three portions 246A, 246B, and         246C fastened together by screws 243, the casing having an axis         of rotation A;     -   a cylinder block 248 and a fluid distributor 250; and     -   a support 254.

The support 254 formed in two portions, namely with a head 256 that closes the motor 242 on a first side relative to the axis A (on the right of FIG. 7), and a portion 258 in the form of a connection arm, that extends in a direction that is substantially perpendicular to the axis A. The end of the arm 258 may be fastened to a machine by means that are not shown for enabling the support 254 to provide a mechanical support for the device 240. In addition, two hydraulic fluid ducts 276 and 280 pass through the arm 258, whereby the support 254 provides, in addition, a fraction of the exchanges of fluid of the motor 242.

The cylinder block 248 of the motor 242 is fastened to the support 254. For this purpose, it has a cylindrical tubular projection 249, which extends concentrically about the axis A on the first side of the cylinder block. The end of this projection 249 is fastened to the support 254 by means (not shown); the projection 249 thus fastens the cylinder block on the support 254.

The portion 246A of the casing forms a cover that closes the motor 242 on the second side of the cylinder block 248 (i.e. on the left side of FIG. 7). This portion 246A includes a central shaft 247 that extends along the axis A while going through a bore 221 of axis A that is formed in the cylinder block. The end of the shaft 247 is situated inside the projection 249 and supports the distributor 250. The distributor is disposed inside a bore 275 of axis A that is formed inside the tubular projection 249. This bore 275 forms a fluid exchange groove that has a function that is described in more detail below.

The casing 246 is held relative to the cylinder block 248 via bearings 264 and 266 that hold the casing 246 in such a manner that they can rotate about the axis A. The bearing 264 is disposed in the bore 221 between the cylinder block 248 and the shaft 247, and the bearing 266 is disposed between the outside surface of the projection 249 and the inside surface of the casing portion 246C.

The pump 244 is arranged inside the head 256 of the support 254. It is identical to the above-described pump 44, except for the shape of its drive part 290. The end of the drive part 290 is arranged in such a manner as to be constrained to rotate with the shaft 247, and thus with the casing 246. The junction between the shaft 247 and the part 290 is formed by a junction part 291.

The fluid exchanges of the device 240 take place in the following manner:

The device 240 has three fluid exchange ducts 276, 278, and 280.

The first duct 278 is formed in part in the head 256 of the support 254 and in part in a pump cover 279. The cover 279 is fastened to the first side of the head 256, i.e. on the side opposite from the cylinder block 248. When the pump 244 is in place in the head 256, the cover 279 serves to block it inside the head 256. The duct 278 connects the delivery chamber 2440 of the pump 244 to an external coupling 274 formed on an external surface of the cover 279.

The ducts 276 and 280 (FIG. 8), formed in the support 254, enable the device 240 to be coupled respectively to the ducts 124 and 22 shown in FIG. 2 via couplings of the support 254 that are not shown. Only the duct 280 (and not the duct 276) appears in the section view of FIG. 7. The end of the duct 280 that is on the same side as the device 240 opens out in the above-mentioned groove 275.

Secondly, the end of the duct 276 that is on the same side as the device 240 is split into two branches. The first branch is connected to the admission chamber 2441 of the pump 244. The second branch opens out (in a manner not shown) into an internal space 252 provided between the distributor 250 and the head 256, which internal space is circularly symmetrical in shape about the axis A.

The groove 275 and the internal space 252 play the same role in the device 240 as the groove 75 and the internal space 52 in the device 40. In particular, the distributor 250 has first and second distribution ducts 282 and 286 that distribute fluid in the cylinders of the cylinder block, in a manner analogous to respective ones of the ducts 82 and 86.

As a result, the motor 242 and the pump 244 operate identically to the motor 42 and to the pump 44. Finally, the output torque of the motor 242 is not delivered, as in the preceding embodiments, via a flange formed on one of the portions of the casing.

In the device 240, a part 223 forming a pulley is fastened to the cover casing 246A. The outside surface of this part includes a ribbed groove 225 adapted to drive a belt. Advantageously, various parts analogous to the part 223 may be mounted in interchangeable manner on the motor 242, so that the motor 242 and in particular the drive groove of said motor can be adapted easily to match the type of belt (or optionally the type of chain or of some other drive member) that the motor is to drive. 

1. A hydraulic transmission device for a machine, which device comprises: a hydraulic motor declutchable by dog clutch, having radial pistons, and including a cam that is secured to a casing, and a cylinder block and an internal fluid distributor that are disposed in the casing; a hydraulic pump including a drive member; and a plurality of fluid exchange couplings; in which device the casing and the distributor are mounted to rotate relative to a stationary support about an axis of rotation, whereas the cylinder block is fastened to said support; wherein the drive member of the pump is constrained to rotate with the casing of the motor, and in that a delivery orifice of the pump is connected to one of said fluid exchange couplings.
 2. A device according to claim 1, wherein the pump and the fluid exchange couplings are situated on the same side of the cylinder block of the motor, relative to the axis of rotation.
 3. A device according to claim 1, wherein, relative to the axis of rotation, the distributor is interposed between the exchange couplings and the cylinder block, and/or between the pump and the cylinder block.
 4. A device according to claim 1, wherein the pump is disposed at least in part inside said support.
 5. A device according to claim 1, including a drive shaft constrained to rotate with the cam and suitable for actuating the pump, which shaft passes through the inside of the cylinder block.
 6. A device according to claim 1, including a drive shaft constrained to rotate with the cam and suitable for actuating the pump, which shaft is fastened to the casing and/or is disposed at least in part inside the support.
 7. A device according to claim 5, wherein a feed passage of the pump, via which passage a fluid feeding the pump passes is formed between the drive shaft and the support.
 8. A device according to claim 7, wherein a feed duct of the pump is formed in the support and connects an internal space of the casing to said feed passage.
 9. A device according to claim 8, including a fluid supply duct making it possible to inject a feed fluid for feeding the pump into said internal space; said internal space being, in addition, connected to said feed passage via a feed duct making it possible to feed the feed passage with fluid; in which device an orifice of the feed duct in the internal space of the casing and an orifice of the supply duct in the internal space are disposed axially on either side of the cylinder block.
 10. A device according to claim 1, wherein at least an admission duct or a delivery duct of the pump and/or at least a feed duct or a discharge duct of the motor passes through the support.
 11. A device according to claim 1, wherein the support is provided with an axial bore formed along the axis of rotation of the motor, and in which the distributor is disposed.
 12. A device according to claim 1, wherein the fluid discharge of the cylinder block takes place into an internal space of the casing.
 13. A device according to claim 1, wherein the support has a portion in the form of an arm through which at least one duct passes and which extends in a direction that is substantially perpendicular to the axis of rotation.
 14. A device according to claim 1, wherein, in order to enable the casing to be coupled to a member to be driven, said casing has a flange, an external groove suitable for receiving a belt, or else a set of teeth for receiving a chain or gearing.
 15. A starter system for a machine having a rotary drive member, in particular for an internal combustion engine, which starter system includes a device according to claim 1 and said rotary drive member, the casing being constrained to rotate with said drive member.
 16. A starter system for a machine having a rotary drive member, in particular for an internal combustion engine, which starter system includes a device according to claim 1 and said rotary drive member, the casing being constrained to rotate with said drive member.
 17. A starter system for a machine having a rotary drive member, in particular for an internal combustion engine, which starter system includes a device according to claim 2 and said rotary drive member, the casing being constrained to rotate with said drive member.
 18. A starter system for a machine having a rotary drive member, in particular for an internal combustion engine, which starter system includes a device according to claim 3 and said rotary drive member, the casing being constrained to rotate with said drive member.
 19. A starter system for a machine having a rotary drive member, in particular for an internal combustion engine, which starter system includes a device according to claim 4 and said rotary drive member, the casing being constrained to rotate with said drive member.
 20. A starter system for a machine having a rotary drive member, in particular for an internal combustion engine, which starter system includes a device according to claim 5 and said rotary drive member, the casing being constrained to rotate with said drive member. 